Defining mechanisms underlying Listeria monocytogenes cardiac infections

描述(申请人提供)：单核细胞增生性李斯特菌(Lm)是一种革兰氏阳性的食源性兼性细胞内细菌病原体，感染人类并在细菌通过肠道屏障移位后导致疾病。虽然健康的人通常表现出轻微的疾病形式，如胃肠炎，但免疫受损的人以及老年患者往往患有更严重的疾病，包括脑膜脑炎和败血症。侵袭性LM感染的后遗症很重要，但文献记载要少得多，涉及心脏；据估计，这种类型的感染至少发生在那些患有侵袭性疾病的人中。最近公布的数据表明，LM菌株的重要亚群具有靶向和侵袭心肌细胞的能力；这是一个具有重要临床意义的新发现。这项提案中概述的实验将检验心脏侵袭性LM菌株已经开发出新的机制和/或表达使它们能够在心脏组织内复制的新的或改变的细菌因子的假设。这些研究将详细了解由LM感染引起的心肌炎的发病机制和成熟过程，并将阐明导致特定宿主组织趋向性的细菌因素。目的1将在动物感染模型中破译LM心脏侵袭性菌株的病理。将使用体内生物发光想象来监测小鼠的细菌感染，以确定心脏感染的进展以及细菌在其他身体部位定植的可能性。实验还将包括对目标组织的组织学检查，以确定宿主免疫细胞渗透的位置，以及使用免疫自旋捕获技术来确定由于宿主对LM感染的炎症反应而发生的细胞损害。目的2将侧重于侵袭性心脏感染相关细菌因子的功能特征。基因和细胞方法将被用来识别与其他疾病的侵袭相比，增强心脏侵袭的LM因子 单元类型。这些研究的最终目标将是建立和确定一个功能特征 目的是建立LM的心脏感染模型，并确定导致选定的LM菌株入侵和破坏心脏组织的能力增强的细菌因素。这些信息将有助于及早识别对患者心脏感染风险增加的LM暴发菌株。最后，本提案中概述的实验将提供重要的 深入了解为特定宿主组织建立细菌趋向性的机制，并将在体内识别宿主炎症反应对感染造成氧化损伤的细胞靶点。 与公共卫生相关：最近证明，食源性致病菌单核细胞增多性李斯特菌的一个重要亚群具有靶向和入侵心肌细胞的能力。这项提案中描述的实验将定义使单核细胞增多性李斯特菌能够在心肌细胞内入侵和复制的细菌因子，这是一个以前与单核细胞增多性李斯特菌感染无关的宿主生态位。这些研究不仅将提供对单核细胞增多性乳杆菌感染所致心肌炎的发病机制和成熟过程的详细了解，而且还将产生一种识别暴发菌株的手段，这些菌株将使暴露于暴发疫情中的个人面临更高的心脏感染风险。

DESCRIPTION (provided by applicant): Listeria monocytogenes (Lm) is a gram-positive, food-borne facultative intracellular bacterial pathogen that infects humans and causes disease following bacterial translocation across the intestinal barrier. While healthy individuals usually exhibit mild forms of disease such as gastroenteritis, individuals who are immune-compromised as well as elderly patients often suffer more severe forms of illness that include meningoencephalitis and septicemia. A significant but much less well-documented sequelae of invasive Lm infections involve the heart; this type of infection is estimated to occur in at least % to 10% of those with invasive disease. Recently published data indicates that significant subpopulations of Lm strains have the capacity to target and invade cardiac cells; this is a new finding with important clinical implications. Experiments outlined within this proposal will test te hypothesize that cardioinvasive Lm strains have developed novel mechanisms and/or express novel or altered bacterial factors that enable them to replicate within cardiac tissues. These studies will provide a detailed understanding of the pathogenesis and maturation of myocarditis resulting from Lm infection, and will clarify bacterial factors that contribute to specific host tisue tropisms. Aim 1 will decipher the pathology of Lm cardioinvasive strains in animal infection models. Bacterial infections will be monitored in mice using in vivo bioluminescence imagining to determine the progression of cardiac infection as well as the potential for bacterial colonization at other body sites. Experiments will also include the histological examination of target tissues to characterize sites of host immune cell infiltration as well as the use of immuno-spin capture technology to definitively identify cellular damage that occurs as a result of the hos inflammatory response to Lm infection. Aim 2 will focus on the functional characterization of bacterial factors associated with invasive cardiac infections. Genetic and cellular approaches will be used to identify Lm factors that enhance cardiac invasion relative to the invasion of other cell types. The ultimate goal of these studies will be to establish and functionally characterize a cardiac model of infection for Lm and to determine the bacterial factors that contribute to the enhanced ability of selected Lm strains to invade and destroy cardiac tissue. This information will be useful for the early identification of Lm outbreak strains that pose increased risk for patient heart infections. Finally, the experiments outlined in this proposal will provide important insight into the mechanisms that establish bacterial tropism for specific host tissues and in addition will identify in vivo cellular targets of oxidative damage resulting from host inflammator responses to infection. PUBLIC HEALTH RELEVANCE: It has recently been demonstrated that a significant sub-population of strains of the food-borne bacterial pathogen Listeria monocytogenes have the capacity to target and invade cardiac cells. Experiments described within this proposal will define the bacterial factors that enable L. monocytogenes to invade and replicate within cardiac cells, a host niche not previously associated with L. monocytogenes infection. These studies will provide not only a detailed understanding of the pathogenesis and maturation of myocarditis resulting from L. monocytogenes infection, but will also generate a means of identifying outbreak strains that place exposed individuals at increased risk for cardiac infections.